Synthesis of methane



Filed Sept. l, 1949 Patented Aug. 17, `195.4

UNITE STATES PAT T" FF ICE, 2,686,819

SYNTHESIS 0F METHANE William B. Johnson, Far Hills,- N. J., assigner toThe M. W. Kellogg Company, Jersey City, N. JL,- a `corporation `ofDelaware Application September 1, 1949, Serial No. 113,50?,VY

16A Claims. 1,.

This" invention relates to a' synthesis of methane from carbonmonoxideand steam; more particularl y it is vconcerned with' a synthesisin which producer gas is the source o'f the carbon monoxide. In thismanner a gas' of lowheating value is converted into one oihigh'B'; t. u.content'.

Producer gas, although easily made from any available type of coal orcoke, is of comparatively limited utility because of its extremely loivgross*` heating. value of approximately 136B.r t. u. per cubic foot.While this `gas is widely used in industry, it is not distributedWithout enrichment to the public", In addition, larger distributionlir'resare` required as` the use of a greater volume of gas is necessaryto furnish any given quantity of heat.` Consequently, there is a needfor an economical process for obtaining a gasof high heating value fromthe product of a sim.-

ple and inexpensive producer gas system. This richer gas shoulddesirably be suitable for mixing with any heating gas in order that itmay serve as an enriching agent for' manufactured gases andas anextenderfor limited supplies of natural gas. Methane is ideal for the purpose inview of its high heating Value, low toxicity and theiclose similarity ofits combustion characteristics to those of" common natural gases.Moreover,.the` proper utilization of methane is already Wellunderstoodby public utility companies',` servicei'nen and gas appliancemanufacturers.

Other processes for the synthesis of hydrocarbons from carbon monoxidehave involved the preliminary removaly of inert-nitrogen from air andthe burning` of coal or coke in relatively purev thesis for methane inwhich the only reactantsv consumed, are inexpensive and readilyavailable. Ai secondobject ofA the invention is to provide an improved"method` for manufacturing a gas of high heating value.

A third object ofthe invention is to provide a method for synthesizingmethane from producer gas `which does'not require-a preliminary removal`A fourth object` offthe invention is to provide a synthesis oiflmethane which does not involve The process of the present invention 2Vburning coal orcoke in substantially pure oxygen.

A nfth object of the invention is to provide a nevv' process for makingmethane in Which substantially'pure hydrogen is also produced.

A sixth object of the invention is to provide an economical, continuous,cyclic process for pro'- ducing methane andhydrogen from inexpensive andreadily available rawmaterials;

Other objects ofthe invention will in part be obvious and Willinpartappear'inthedetailed description hereinafter.

The present invention concerns a cyclic process for synthesizingAvmethane from carbon monoxide; preierably'furnishedby pr'oducer'gas, andsteam in which a carbide-forming metal' is re'- acted with steam at asufficiently high temperature to producev hydrogen and an oxide of themetal. The metal oxide is then c'arbided with carbon monoxide at alsuitably elevated temperature' and the metal carbide is reduced with theaforementioned hydrogen at a temperat'ure'high enough toprodnceinethaneand regenerate the metal. The invention accordinglycomprises the several steps and the relation of one or more of suchsteps with respect to each of the others thereof, which vvilly beexemplified in the method hereinafter disclosed; and the scope` of thelinvention will be indicated in the claims.

The process of the present invention consumes only air, Water and eithercoal or coke in producing methane and hydrogen,` for theY metal inpowdered forni is regeneratedl and recycled, while the hydrogen requiredin one step is pro` duced in excess in ano-ther reaction- Moreover,

no extreme temperatures are encountered, sincethe' coal or eolie may beburnedin air rather than substantially pure oxygen. Nitrogen and' otherinerts, as Well as carbon dioxide, areeliminated, inexpensively and"Without difficulty byI merely venting allgaseons productsof thecarbiding reactionto the atmosphere; alternatively, some or all of thenitrogen may be recovered in rela tively pure forni".` All of thechemical changes described hereinafter are exothermic'and the Wateremployed as a coolant in a variety of heat' exchangersprovidcs'- a morethan ample supply of steam for the `oxidation stepA In the preferredprocess #the oxidation; carbiding andlreducticnreactions are carried outsimultaneously and continuously in different reaction zones` bycirculting the fluidized solids through the system.

The base metal employed in the process is a reactant' and` not acatalyst in the true sense of the term. Nevertheless, catalysts maybeiadvantageously used along with the carbide-forming metal inpracticing the present invention, for they permit the carbidingoperation to be conducted at lower temperatures. Examples of suchcatalysts include manganous oxide, manganese dioxide and copper, amongothers; and they are used in small quantities, as for instance 1% or 2%by weight of the metal reactant.

Promoters in small amounts ranging up to 1.5 of the weight of the basemetal may also be added to the carbide-forming metal or to the mixtureof metal and catalyst. These substances increase the carbon content ofthe metal carbide, thereby permitting a reduction in the quantity ofprimary metal employed in the process. Non-volatile alkali and alkalineearth oxides, as for instance the oxides, hydroxides and carbonates ofpotassium, sodium, calcium, strontium and barium are suitable promoters.In general, it may be said that any catalyst or promoter which has beensuccessfully used in the Fischer- Tropsch synthesis will produceequivalent effects in the present process.

Any metal capable of forming a carbide may be utilized in thissynthesis. Iron, cobalt, nickel,

zinc, manganese, chromium, tin, and molybdenum constitute only a few ofthe metals available for the purpose. The first three named, which makeup the fourth period of groupv VIII of the periodic table of elements,appear superior to the others, and iron is the preferred metal by reasonof low cost and high activity. Best results are secured when the metalis in fluidized form in order to obtain the advantages inherent in acontinuous, cyclic, luidized process in which the solid reactants arerapidly circulated while suspended in streams of gaseous reactants, andiiow under the influence of gravity like pseudoliquids developingpseudo-hydrostatic uistatic pressures after separation from the gasstreams. Fluidized operations not only provide superior control ofreaction temperatures but also afford maximum surface Contact betweenthe reacting gases and solids. Moreover, due to the increased surfacearea of the fluidized solids, their chemical activity is enhanced andall of the reactions involving them are carried out at lowertemperatures than is the case with larger particles.

For the application of the fiuid technique described herein, the powdershould all pass through a Ai-mesh screen. But to reduce the minimumtransport velocity in the reaction coolers and to minimize bridging orblocking during gravity flow down the hoppers and standpipes, it isdesirable to have a range of particle sizes averaging about 200-mesh orfiner.

The temperatures of each of the three reactions involving a metal orcompound thereof vary with the different carbide-forming metals; thoserequired for iron, cobalt and nickel are set forth below. Pressuresranging from atmospheric to 50 pounds per square inch gage (p. s. i. g.)are recommended for all three reactions, but higher pressures, up to say500 p. s. i. g., may be justified in order to increase reaction rates orpermit the use of smaller and less expensive equipment.

As the source of carbon monoxide, producer gas is preferably employed inthe instant process; its production is exemplified in the followingequation:

I. Air (7O2-}-26N2)|14C 14CO+26N2 Water gas may be substituted but isless satisfactory inasmuch as the relatively large quantity of hydrogenpresent reduces the carbon efciency in the carbiding reaction. For thesame reason,

coke is a better fuel for the producer than coal inasmuch as coalproducer gas contains a minor amount of hydrogen.

Carbon monoxide from any other source may be used provided there are noexcessive quantities of impurities which will inhibit or interfere withthe carbiding reaction described below unless such impurities can beremoved in a commercially feasible manner.

In another step a carbide-forming metal at an elevated tempera-ture isoxidized with steam to produce a metal oxide and hydrogen.

the temperature be maintained between 950 and 1050 degrees Fahrenheit.

The oxide, such as iiuidized ferrosic oxide, is then reacted with theproducer gasv to form a metal carbide.

This reaction proceeds very rapidly and a more active carbide resultswhen pressures ranging from atmospheric up to 30 p. s. i. g. areemployed. It is thought that a variety of carbides of the selected metalare actually produced, especially when ferrosic oxide is involved.However, the carbon content of the mixture of iron carbides appears toapproximate that of ferrous carbide and the product may be regarded asferrous carbide for all practical purposes. yIhe nitrogen in theproducer gas is inactive in this reaction and the only effects due toits presence arise from its reduction of the carbon monoxide partialpressure. In this instance only the solid resultant is essential in thepresent process, so the gaseous products as well as inert gases areusually vented to the atmosphere. However, a portion of the exhaustgases may be scrubbed free of carbon dioxide in any suitable manner toprovide substantially pure nitrogen which may be added to the excess ofalmost pure hydrogen produced in reaction II to form a satisfactory feedfor an ammonia synthesis plant. In addition, the carbon dioxide may berecovered from the absorption liquid and recycled back to the gasproducer where it will be reduced by the incandescent coke to carbonmonoxide thereby increasing the carbon efciency of the process.

The yield of metal carbide is substantially that of theory when anexcess of ferrosic oxide is employed. Where the carbon monoxide is inexcess, an undesirable deposition of carbon on the ferrous carbideoccurs. Not only does this reduce the carbon eiciency of the process,but it also retards the subsequent reduction of the metal carbide tomethane and iron. An excess of ferrosic oxide on the other handincreases the carbiding rate and this excess of solids permits bettercontrol of heat transfer throughout the system without interfering withthe other reactions of the process cycle. Thus, a deficiency of theoxide is disadvantageous and it should be present in at leaststoichiometric proportions or an exassetato emrbly sthe iexcessfoflferrosicuoxid'e aamounts` to very fastreactionrate .notslowed down` asitlis in the rcasewol? a dense :phase 1 xed 1' or circulating bedrefierrosicbxide where `the lrateis reduced by the .introduction zofcarbon .monoxide into solidsor'sub-normal:activitydue to theirsubstantial fferrous carbide `content and also by'the increasingconcentration oftcarbonldioxide as Ithe gase'szrise throughcthetbed. l i

iSuitable temperature ranges ifor the .carbiding operation aref450 toS800 degrees Fahrenheit in theicase Iof iron, 550 to 650::1degreesFahrenheit being preferred, and .300 hto `e500 degrees Fahrenheit riorseither fcobalt or nickel. AI owering the temperature favors `thereaction equilibrium while `raising it increases ythe .reaction rate.

`.cN-ext the metal carbide is reacted I'with all or a portion of `.thehydrogen ,produ-ced iin reaction II. Thefhydrogen reduces the .carbideLto the metal and `'combines with the carbon liberated to form methane.l i

lBle'zC#SH2-1'le"-I-SCI-Ifl` Moderately elevated `pressures `of a fewatmospheres favor the reaction, while higher pressures tend :to yieldhigher hydrocarbons than methane. With `stoichiometricl .proportions `ofreactants this fairly rapid1reaction `proceeds to over 95% ofcompletion, and where hydrogen i-nfa `clesirable `excess of about isused, the yields aare very close to "that oi' theory.` It will be notedthat the hydrogen ,produced in .reaction II amounts `to one-third :morethan is `requiredfor reaction IV,and all of this excess may p beemployed in the latter reaction where `a `prod-- uctggas ofsomewhatlower heating value islacceptable. The `operative temperaturerange `for iron extends `from 650 to 950degrees Fahren? heit" and thelatter tgure shouldnot `be exceeded inasmuch as iron beginsto soften andbecome somewhat tacky at 1950.1degrees. :For :iron `the recommendedtemperature range isfrom I'i50to 8D01degrees Fahrenheit. Considerablyless heat is Arequired for cobalt.or nickelas the temperaturecmay .rangefrom `400 to `600 degrees Fahrenheit. 1

The invention is best understood .byreference to `the accompanyingdrawing "which is `a .flow sheet of the-novel process initsjpreferredform` iig-ure is, purely schematicinnature and isnotlintendedto illustrate the optimum locations orldirnensions of any oftheapparatus depicted.

.Air .from the blower 1| issupplied` through valved Yline 2to-gasproducer 3` Whichis preferably -`f theslagging type. The coke orcoal feed for the .producer `enters throughhopper li and the producergas passes through line E to a waste yheat boiler `l whereit gives `up`most ofits heat. Leaving through line l., the gas passes toacycloneseparator 8 in which `ily ash is removed trom the gas stream.`Pipe!) carries the `gas to a scrubber 'I0 Where it is scrubbed withisrinsuni'cient to iinterfere with :the subsequent reaction withferrosic oxide.

1CNext the .gaseousmixture consisting :chiefly of nitrogen and carbon4.monoxide nproceels throu'g-hpipe I I 3 .into transport uline JM fwhere the hot uidized .ferrosi'c .1oxide, usually 1in "stoichiometricexcess, is injected 'Jfrom standpipe I5 attached to a sealed vessel |16Sand controlled by-1a slide `valve ll. If necessary r4alsmall `quantityVof a .suitable .aerat'ing iagent, "such `assteam, 4may be introducedinto vpipe I 5 `and Salso yat the bottomfo'f hopper LI-Ieatl onecor morepoints to maintain th'elinely divided `ox-ide -in fl-uidizeolJcond-ition. .As -the up owdered 1. oxide lsweeps l up through in'e fillias tra Tdilute .turbulentsuspension -in -the carrier stream of gases`an Ivexothermic [reaction eoinmencesmin which the lcarbide `.of ithemetal i'sciiiormed. `Theudensity ofthe 'suspensioninthis carrier `lineis a function-pf ith'e static .pressure and the preferredrangeis `from6:3 to 5.0 lbs/cu. it. `"The i cptimumuvelocity of Athe-umixture`is-about 20lto `30 Lft/sec. Suchconditionsarereadily obtained by `knownldesign principles in selecting the proper pressure drop :through `.pipeE4 `and choosing aniinternaldiameter for this -lineadei`quatewfor.theliiow ratesoffreactants. flhefh'eat Fahrenheit. for the.producer gas is notfar` above atmospheric temperature. `A `water-cooled`re action cooler `Itis .provided Ato.Imaintaina @reaction`ten'lperaturefof-550m 650 degrees Fahrenheit...n this vessel, thereaction zone -is Ylof greater crossesectional area 'than line`-lf1l,\thereby reducing the .velocitycof fthe-suspension `to Labout 3 ito i0 `iii/sec. andi'ncreasingits density to approximately 20 tofiOlbs/icu. it. Thel'ength of thisreaction zone is. of course determinedlby the requirements .of adequate ytime for the lreaction and sufficientheat transfer area to `maintain the reaction temperature `withir-i'thelimits "indicated. `Line. i5? whichcarries `thel'mixture lintothe closedvessel `2li fextends welldown into the fin terior but not fbelow thesurface =of thedense bed (approximately fZ0-fto 100 lbsf/cuQt.) of ironcarbide 1 and l excess vierrosic i oxide stored therein. At `this `pointthewgases 1in `the mixture, chiefly carbon dioXideand Lnitrogen under a`pressure of A20 to 30 p. s. i. fg., separate Lfrom the finely dividedsolids, and the settling `or separation efciency lis i enhanced greatly`by `the `downward discharge oi' the suspensioninto-settlerf. Thediameter-:of `this vessel -is `selected to provide an upwardvelocity ofgases therein of from 1-'to 2 it./sec. 'and lits length 'is designed tofurnish storagespacei'or-an amplevsupply lof the metal compounds plus`suicient disengaging space thereabove toattain the optimum gravitylseparationoi powder from thegases. The gases are exhausted to the`atmosphere through a filtering device -2`i `and 'exhaust pipe "22. Anyentrained iine particles are removed by the "filter, whichis preferablyo'f porous metal or ceramic:construe--` tion, and consists oi severalsections. n lvalve arrangement operated by an automatic time cyclecontroller (not shown) is.provided=to1clear the filter of adheringpowder by blowing back the exit .gases through each `sectionofthe-filter in succession.` `This mechanism Lis so 4Iadusted as to always`be clearing ione section of the-filter while the other sections-arelltering the exhaust gases. lIrffa cycloneseparator'isusedin placeof be passed through a Water scrubber to avoid the loss of fines.

' In the event that either the nitrogen or carbon dioxide in the exhaustgases are to be recovered, line 22 is connected to an absorber orscrubber (not shown) where the carbon dioxide is dissolved by passingthe gases through any suitable absorption liquid from which the carbondioxide may later be recovered. The absorber eiiluent consists ofrelatively pure nitrogen contaminated with the rare gases of theatmosphere in small amounts along with lesser quantities of unreactedcarbon monoxide and perhaps hydrogen.

The hot metal carbide and oxide, at a temperature only a few degreesbelow that in reactor IB, descend from tank 20 through standpipe 23controlled by slide valve 24 into a rapid currentof hydrogen in line 25.Any aeration necessary for tank 20 or pipe 23 can be supplied by fluegases or by compressing and recycling the effluent from line 22. Thehydrogen employed in this step is produced in excess in the oxidation ofthe metal as described hereinafter. Since this gas is comparativelycool, the hot solids furnish all or most of the heat required to startthe rapid exothermic reaction. In pipe 25 and enlarged reaction cooler2G, which maintains the reaction temperature between 750 and S degreesFahrenheit, the metal carbide in the suspension is reduced while inconcurrent flow to iron and methane by the hydrogen which is preferablypresent in stoichiometric excess. This powdered iron and ferrosic oxidesuspension is then discharged by line 2l just above the bed of solids inhopper 2t where the pressure is in the to 30 p. s. i. g. range. Themethane and any unreacted hydrogen separate from the powder and leavethrough filtering device 29, similar to filter 2l. Thereafter theproduct gas is passed through pipe 30, cooler 3i and then to suitablestorage facilities.

From the bottom of vessel 28, where the density is of the order of 70 to100 lbs/cu. ft. and its temperature only slightly below that of reactioncooler 2t, the hot iiuidized metal and excess oxide iiow dov/n standpipe32 controlled by slide valve 33 to carrier line 34 and are there pickedup by a swift, valve-controlled stream of steam from the boiler t orreaction coolers. The turbulent suspension of reactants passes throughenlarged` reaction lcooler 35 maintained at 950 to 1050 degreesFahrenheit and the powder is deposited by pipe 3B in tank I6 on top ofthe layer of metal oxide which has a density of about 50 to 80 lbs/cu.it. The steam enters transport line 34 at a pressure equal to the 20 to30 p. s. i. g. maintained in hopper 9&5 plus the designed pressure dropbetween the bottom of standpipe 32 and hopper N. Its temperature isadjusted to the yminimum required to initiate reaction with the iron inthe powdered mixture to form hydrogen and ferrosic oxide while intransport to the receiving hopper.

The hydrogen and excess steam leave tank I6 through the cyclone oriilter 3T which separates the nes. Since the steam constituent of theeii'luent in pipe 38 will inhibit the reduction of iron carbide byhydrogen in the following step of the cycle, as much moisture aspossible iS condensed out of the mixture in a water-cooled condenserfrom which the condensate leaves by trap line 40 while the hydrogenpasses up pipe 4l. By suitable adjustment of valve 42 some or all of theexcess hydrogen may be drawn off, if desired, through `line 43 as asubstantially rates.

pure product while the 'remainderis recycled through pipe 44 andcompressor 45 totransport line 25 for the reductionstage of the process.Any excess hydrogen'recycled through the reduction step is not lost andwill be recovered along with Vthe methane from cooler 3l.

Where it is necessary, to aerate the bottom of tank 28 and/or line 32,this may be accomplished with either some of the excess hydrogen frompipe 43 or 44 or product gas from cooler 3l.

In maintaining the desired concurrent flow in all three reactionsinvolving fluidized solids, the maintenance of approximately equalvelocities in carrier lines I4, I9, 25,21, 34 and 36 of from 20 to 30ft./sec. is recommended and the densities in these lines are from 0.3 to5 lbs/cu. ft. depending` on reaction pressure. .The velocities inreaction coolers IS, 26 and 35 are preferably 3 to 10 ft./sec. and thesuspensions there have densitiesk of 20 to 40 lbs./cu. ft. In settlersor hoppers I6, 2li and 2S, upward gas velocities of from 1 to 2ft./sec..are preferred. These velocities are obtained by designing thisequip-V ment along the linesv indicated previously.

The proper lengths of standpipes l5, 23 and 32 are determined inconventional manner to produce sufficient fluistatic pressure to injectthe solid reactant into the carrier lines at suitable Since none of thei hoppers may collect fiuidized solids at a greater rate than the othersettlers overan extended period without throwing the` system out ofoperating balance, it is apparent that `the flow rates of solids,calculated as Fe, down each of the three standpipes `must be equal inthe long run. Therefore, the operating adjustments on the plant toattain the desired velocities and stoichiometry will be made on theiiuid reactants by means of the valves inV lines 2, 44 and the steamline.

In the event that it proves desirable to achieve better control ofreactant temperatures, this may be readily accomplished by theinstallation of heat exchangers in one or more of the reactant supplylines (the standpipes and pipes I3 and 44) to heat or cool the reactantto the desired ligure.

The process described above is cyclic and involves the rapid circulationof iiuidized solids with the various reactions occurring simultaneouslyand continuously in different reaction zones. This represents thegreatly preferred form; Nevertheless, it is readily apparent that theprocess can be performed in an intermittent manner with all reactionsoccurring in sequence in a single reaction zone,or alternatively infixed beds of solids in three reactors using known cycle controldevices. In such cases, the particle size of the solid reactant mayrange from the fine powders discussed hereinbefore up to granules ofapproximately diameter. However, it is to be understood that theeiiiciency of the intermittent cyclic process is considerably below thator" the continuous circulatory one because the reactor or reactors wouldnecessarily be kept at a single average temperature rather than in theoptimum range for each of the reactions and the temperature control in awide fixed bed is inferior to that obtainable in a turbulent circulatingsuspension of the solids in a relatively narrow stream of gas. Where thefixed bed consists of granular rather than fluidized solids, thevariations in temperature in various parts of the bed are far greaterand higher reaction temperatures are required. In addition the operatingcosts of the intermittent process would obviously be much greater thanthe circulating continuous process. Y

thesis of methane from carbon monoxide and steam which comprisesoxidizing a suspension of a carbide-forming fluidized metal obtainedfrom the reduction step mentioned hereinafter with a carrier stream ofsteam at a temperature sufficiently elevated to produce principallyhydrogen and an oxide of the metal, separating the hydrogen and saidmetal oxide, reacting a suspension of said iiuidized metal oxide with acarrier stream of carbon monoxide at a temperature sufficiently elevatedto produce a carbide of the metal, separating said metal carbide fromthe gases in the reaction products, reducing a suspension of saidfluidized metal carbide with a carrier stream comprising at least aportion of said hydrogen at a temperature suiciently elevated to producethe metal and a gasiform mixture comprising chiey methane, andseparating the iiuidized metal and the methane.

15. A continuous cyclic process for the synthesis of methane from carbonmonoxide and steam which comprises oxidizing a suspension of fiuidizediron obtained from the reduction step mentioned hereinafter with acarrier stream of steam at a temperature of from 700 to 1200 degreesFahrenheit to produce principally hydrogen and ferrosic oxide,separating the hydrogen and ferrosic oxide, reacting a suspension of thefluidized ferrosic oxide with `a carrier stream of carbon monoxide at atemperature f from A450 to 800 degrees Fahrenheit to produce a carbideof iron, separating said carbide of iron from the gases in the reactionproducts, reducing a suspension of said fluidized carbide of iron with acarrier stream comprising at least a portion of said hydrogen at atemperature of from 650 to 950 degrees Fahrenheit to produce iron and agasiform mixture comprising chiefly methane, and separating thefluidized iron and the methane.

16. A continuous cyclic process for the synthesis of agas of highheating value Vwhich comprises burning carbonaceous matter in arestricted quantity of air to form producer gas, oxidizing a suspensionof yluidized iron obtained from the reduction step mentioned hereinafterwith a carrier stream of steam at a temperature of from '700 to 1200degrees Fahrenheit to produce principally hydrogen and ferrosic oxide,separating the ferrosic oxide and the hydrogen, reacting a suspension ofthe uidized ferrosic oxide with a carrier stream of producer gas at atemperature of from 450 to 800 degrees Fahrenheit to produce a carbideof iron, separating said carbide of iron from the gases in the reactionproducts, reducing a suspension of said fluidized carbide of iron with acarrier stream comprising at least a portion of said hydrogen at atemperature of from 650 to 950 degrees Fahrenheit to produce iron and agasiform mixture comprising chiey methane, and separating the fluidizediron and the methane.

References Cited-in the le of this patent UNITED STATES PATENTS NumberName Date 2,130,163 Tiddy et al Sept. 13, 1938 2,364,123 Benner Dec. 5,1944. 2,369,548 Elian Feb. 13, 1945 2,409,235 Atwell Oct. 15, 19462,449,635 Barr Sept. 2l, 1948 2,537,496 Watson Jan. 9, 1951 2,544,574Walker et al. Mar. 6, 1951 FOREIGN PATENTS Number Country Date 13,861Great Britain June 15, 1907 OTHER REFERENCES Bahr et al., Berichte(July-Dec. 1933), pages 1238 to 1241.

1. A CYCLIC PROCESS FOR THE SYNTHESIS OF METHANE FROM CARBON MONOXIDEAND STEAM WHICH COMPRISES REACTING A CARBIDE-FORMING METAL OBTAINED FROMTHE REDUCTION STEP MENTIONED HEREINAFTER WITH STEAM AT A TEMPERATURESUFFICIENTLY ELEVATED TO PRODUCE PRINCIPALLY HYDROGEN AND AN OXIDE OFTHE METAL, REACTING CARBON MONOXIDE WITH SAID METAL OXIDE AT ATEMPERATURE SUFFICIENTLY ELEVATED TO PRODUCE A CARBIDE OF THE METAL, ANDREDUCING SAID METAL CARBIDE WITH A LEAST A PORTION OF SAID HYDROGEN AT ATEMPERATURE SUFFICIENTLY ELEVATED TO PRODUCE THE METAL AND A GASIFORMMIXTURE COMPRISING CHIEFLY METHANE.